More fertile couples are finding it pays to be surrogates.

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Brent Bell is packing lunches for school, bologna-and-cheese sandwiches for his two boys, peanut-butter-and-honey for his daughter. Between asking 8-year-old Liam if he wants his orange peeled and chastising 12-year-old Klaire for not eating her last sandwich, he pulls down an ultrasound photo tacked to the fridge. The black-and-white image of two beating hearts is labeled twin a and twin b. Brent's wife, Lisa, 35, is about 10 weeks pregnant, and already her resolve is being tested.

She started out with triplets but lost one to an ectopic pregnancy. The embryo growing outside her uterus gave her such piercing stomach pains that Brent, 33, had to take her to the obstetrician and then to the hospital, where surgeons worked to repair a ruptured Fallopian tube. "I was shitting bricks," Brent says. He leans down and opens a drawer to retrieve a 22-gauge needle, which his wife uses for her daily injections. "Are you familiar with the needles they use on farm animals?" he asks. The twins Lisa is carrying do not belong to him. They're not hers, either, which means for the first trimester she has to shoot progesterone—in a liquid the consistency of honey—into her butt or thighs to help the placenta stick to the uterine wall. "She has to push so hard I can see her hand shaking," Brent says. When she's done, an imprint from the plunger is visible on her thumb.

All of this pain and suffering come with the job: Lisa is a surrogate mom hired by a couple in Sweden to carry the babies to term. Brent will tend to her aches and cravings along the way, just as he did when he was the one who had knocked her up. For their combined labors, the two will receive at least $20,000.

Shirley Zager, director of Parenting Partners, a surrogate service in Chicago, estimates that there have been about 28,000 such births in the United States since 1976. The women who make them possible are almost always married to guys like Brent, men who are comfortable pimping out their wives' bodies for nine months at a stretch.

Brent, who's six feet six and wears black wire glasses, isn't some hayseed with dollar signs in his eyes. He drives each day from his home in Joplin, Missouri, to nearby Baxter Springs, Kansas, where he works as a supervisor at a food-manufacturing company. He likes Johnny Cash and Metallica. He met Lisa at Missouri Southern State University, where the two shared an interest in theater.

It was bighearted Lisa's idea to birth babies for couples who could not do it for themselves. Brent didn't warm to it right away. He approached it as a business. "I wanted to know how much this was going to cost and what money was going to come in," he explains. But after speaking to the first would-be father, a man about 10 years his senior, on the phone, he changed his mind. "An hour into it, it was just two guys talking," he says, "one who wanted kids and one who had a wife who could have kids."

It's important for husbands to embrace the decision, says William D. Petok, a Baltimore psychologist who evaluates surrogates. He likes to meet with candidate couples to look for signs of reservations. He's never seen a case in which surrogacy was the guy's idea. "A husband wouldn't wake up and say, 'Honey, I think this is what you should do,'" he says. "That's almost inconceivable."